Hongbin defended west Suiyuan, especially Wuyuan in 1940 against the Japanese. Ma Hongbin commanded the Muslim 81st corps and incurred heavy casualties, but after fierce fighting eventually repulsed the Japanese and defeated them. Unable to withstand the pressure of Chinese attacks, the Japanese at Wuyuan retreated on March 30 and 31. On April 1 a guerrilla force and cavalry column recaptured Wuyuan, and the 11th Provisional Division recaptured Wu-pu-lang-kou. On April 3, cavalry recovered Xishanzui as the Japanese retreated to the east. Japan used poison gas against the Chinese armies at the Battle of Wuyuan and Battle of West Suiyuan. Sources Hsu Long-hsuen and Chang Ming-kai, History of The Sino-Japanese War (1937–1945) 2nd ed., 1971. Translated by Wen Ha-hsiung, Chung Wu Publishing; 33, 140th Lane, Tung-hwa Street, Taipei, Taiwan Republic of China. p. 319-334, "Chinese Winter Offensive" (Late Nov 1939 - Late March 1940) Map 19. External links Maps of Wuyuan battle area during World War II Wu-Yuan nk49-7, Hsi-Nao-Pao nk49-10 Conflicts in 1940 Wuyuan 1940 in China 1940 in Japan History of Inner Mongolia March 1940 events April 1940 events